Friday, December 6, 2019

Why Oak?: Material Choice in British and Irish Logboats

(This post is slightly revised from a paper submitted for a class in Materials, Technology and Social Life at University of Southampton, 2018.)


Referring to wooden tubs, buckets, flasks, and cups recovered at Sutton Hoo, Comey (2013:109) wrote, “A fundamental aspect of any wooden object is the species of tree or woody shrub from which it originates. Identification of species is an important consideration for understanding these wooden vessels and this is true of all archaeological wood….”

The consideration is important because material choices reflect cultural decisions and practices (Conneller, 2011). The act of producing any wooden object is mediated through and by the material. Obtaining the wood, producing and selecting appropriate tools, and the techniques or methods employed to work it – all steps in the châine opératoire – are cultural acts influenced by the material (Hurcombe, 2014). The finished object thus reflects culture independently of the use to which it is put. As described by Conneller, “materials are meaningful and these meanings are reciprocally generated in the varied processes of people’s engagement with them. Tracing these connections reveals past worlds” (2011:9).

Logboats are the largest and most technologically sophisticated portable objects recovered from pre-Bronze Age Britain and Ireland (Figure 1). Introduced in the Mesolithic or Neolithic, they remained in use in the Atlantic Archipelago until the second half of the second millennium AD (Gregory, 1997:23-24; Lanting, 1997), fulfilling important economic and social functions in a range of applications, including transportation, fishing, and warfare. With wood types and dates known for hundreds of archaeologically-recorded logboats (Lanting, 1997-1998), an analysis of the choice of wood used in their construction might prove revealing of “lost worlds.”

Figure 1
Discovery of the Brigg logboat.
Discovery of the Brigg logboat. At 14.78 metres long and an estimated 2,809 kg (McGrail, 1978a:171), it was the largest logboat in the archaeology of Britain and Ireland. (image: Illustrated London News, 1886. Click any image to enlarge.)
Although dozens – perhaps hundreds – of additional European finds have been made in the more than two decades since Lanting’s summary and analysis of logboat dates (1997), I have not updated his list, believing that the patterns he identified are unlikely to change significantly by the addition of the new data. Likewise, patterns present in the summary works of McGrail (1978a, 1978b, for England and Wales), Mowat (1996, for Scotland), Gregory (1997, for Ireland and Scotland), and Fry (2000, for Northern Ireland) are assumed to remain substantially unchanged and no attempt has been made to gather new data specific to Britain and Ireland, other than by reference to Lanting (1997-1998).

A Preponderance of Oak

Wood types identified in archaeological logboats in Britain and Ireland are summarized in Table 1.

Table 1
Archaeological Logboats by Wood Genus, Britain and Ireland

England and Wales1
Scotland2
Ireland
Total

#
%
#
%
#
%
#
%
Oak
76
96
58
92
1683
98
302
96.5
Pine
1
1.3
5
8


6
1.9
Elm
1
1.3




1
0.3
Ash
1
1.3




1
0.3
Alder




24
1.1
2
0.6
Poplar




14
0.6
1
0.3
1 McGrail, 1978a:309
2 Gregory, 1997:162
3 Gregory, 1997:162
4 Lanting, 1997-1998-1998:628/table 1

Non-oak boats that have been reliably dated are shown in Table 2. Where a range of dates was available, the mean is shown.

Table 2
Dated Archaeological British and Irish Logboats by Wood Genus (non-oak only)
Location
Date BP
Wood type
Ireland


Carrigdirty, Co. Limerick
5820±40
poplar
Derrybrusk 1
2876±34
alder
Derrybrusk 2
2912±38
alder
Britain


Giggleswick Tarn
650±30
ash
Warrington 11
950±90
elm
(Lanting, 1997-1998-1998)

The preponderance of oak in the record is striking and calls for investigation. Was oak simply the best choice, everywhere and always?

According to McGrail (1978a:117), the “ideal tree” for the construction of a basic logboat has the following characteristics:
  • “Long straight bole of substantial girth and little taper, with straight grain and no recent branches low down.”
  • durable, resistant to rot, easy to work, strong, lightweight
  • located where it can be easily and safely felled and readily moved to a water-course
McGrail goes on to state, “Of the species of timber available during the past 6000 years in north-west Europe, forest-grown oak (Quercus sp) appears to be the nearest to the ideal for logboat hulls” (1978a:117). This statement is subject to amendment, as will be seen below. For the moment, it is sufficient to observe that it would be remarkable if the “ideal tree” for more than 90 percent of logboat builders throughout Britain and Ireland had been of a single genus, readily available over the course of nearly 6,000 years and always growing in a convenient location for felling and easy transfer to the desired watercourse.

Five possible explanations might account for the preponderance of oak:
  1. With few exceptions, oak was the only suitable timber available for logboat building.
  2. Oak is represented disproportionately because other woods decay more rapidly out of the archaeological record.
  3. Oak is represented disproportionately for reasons other than decay resistance – for example, because of the fortuitous nature of many logboat discoveries.
  4. Oak is functionally superior to other timbers to such a degree that it was the only logical choice.
  5. Oak was preferred for reasons other than functional ones – i.e., wood choice was influenced by ideological considerations.

Timber Availability

In the “fully developed wildwood” of 5500-3100 BC, six different forest communities were present in British Isles:

1.      Pinewoods: central Scottish Highlands, localized in Lake District and Fens, certain mountains in Ireland
2.      Birchwoods: Scottish Highlands, other Irish mountains, locally in southern Scotland, Lake District, Wales, southwest England
3.      Hazel and elm woods: most of Ireland, locally in Wales and southwest England
4.      Oak and hazel woods: western Ireland “and the rest of the Highland Zone of Great Britain.” A variant of this community in northern England included ash.
5.      Lime: predominant across lowland England and north to Lancashire. The second-most common tree in limewoods was variously oak, hazel, or ash.
6.      Alder: Throughout Britain but rare in Scottish Highlands, western Ireland and southwest England (Rackham, 1980:99, 1995:28-32).


Beginning in the Neolithic, forests throughout Britain and Ireland were cleared for agriculture and swine forage (Rackham, 1995:33-34). Forestry practices to ensure a consistent supply of “wood” (i.e., small stuff suitable for building hurdles and making charcoal, for example, as opposed to “timber” for heavy construction) – were “widespread and ancient by the time of the Domesday Book (1086)” in England (Rackham, 1980:3), although this practice of “woodmanship” did not become common in Scotland until perhaps the 16th century (Rackham, 1980:6).

After 1251, oak was “(b)y far the commonest timber tree in nearly all kinds of woodland” (Rackham, 1980:145). It is important to note the qualifier “timber” in this statement. Starting in the Neolithic, many trees that were not valued as timber were coppiced to produce a steady supply of “wood” and constituted major components of many woodlands (Rackham, 1995:38, passim). Had they been valued for construction purposes, trees such as alder and poplar could have been allowed to grow to timber.

Little oak grew in the Scottish Highlands, but Scots pine was among the major forest communities there (Rackham, 1980; Mowat, 1996:6, 114-115, 129). Gregory states that oak was the only readily available, suitable tree for logboats in Ireland (1997:168-170), but this ignores alder and poplar, both of which are native (Tree Council of Ireland, no date a, no date b). As in the case of Britain, alder, poplar, and perhaps other genera might have been used, had they been managed for timber.

In summary, other tree types suitable for the construction of logboats were available across much of Britain and Ireland throughout the logboat era. Logboat builders’ material choice was not limited to oak by lack of alternatives.

Differential Preservation

Differential preservation was mooted as an explanation for the preponderance of oak in the archaeological record in the first modern, comprehensive study of logboats in the region. Writing of England and Wales, McGrail stated, “allowance must be made for possible bias in the survey, due to oak’s greater durability” (1978a:309. See also Rackham 1980:18; Rogers, 2011:196).

Others have noted that several of the earliest boats in the records of Europe and the British Isles are of non-oak genera, concluding that these other woods would probably appear more frequently in later finds had they been used (Gregory, 1997:168, 171; Lanting, 1997:631; Rogers, 2011). Instead, the record shows not differential preservation, but an evolution in wood choice. “The oldest logboats, from Pesse (NL), Nandy l and 2 (Fr) and Noyen-sur-Seine (Fr) are made of pine. This is certainly not a coincidence. Before 8000 BP, in northwestern Europe pine was the only tree of sufficient length and diameter available for this purpose. During the Later Mesolithic a clear preference existed for soft and easily workable wood such as lime, alder and poplar/aspen” (Lanting, 1997-1998:645). Oak becomes common in the record only with the arrival of the Neolithic.

In summary: if the record is skewed toward oak by its superior resistance to rot, any such effect is likely to be small. Given the size of Lanting’s survey (considering more than 600 dated logboats), the possibility that the record is skewed substantially by random factors of discovery is also small.

Functional Considerations

Oak is an excellent boatbuilding wood. It is hard, strong, durable, and it does not absorb water readily (Boulton and Jay, 1944:54; McGrail, 1998:26). Forest-grown trees tend to be tall and straight and without low branches so that, given sufficient time to build girth, they produce boles highly suitable to logboat construction (McGrail, 1998:26). According to Rogers, “In comparison with other species, oak has an ideal combination of size, grain, strength, workability and durability for building logboats” (2011:196).

This overstates the case. Workability varies considerably from tree to tree (Boulton and Jay, 1944:55), and oak logboats can be carved with hand tools only while the wood is green, as seasoned oak is too tough (Gregory, 1997:60-61). Fresh oak will not burn (Gregory, 1997:65, 71; but see Arnold, 2006, cited by Rogers, 2011:196, for possible exceptions), precluding the use of fire as a transformative tool.

Oak’s reputation for workability is, in fact, so dependent upon the availability of metal tools that it was formerly believed that oak logboats could not be built with stone tools (Rogers, 2011:196. See also Godwin and Deacon, 1974:60-61). Only late in the 20th century were oak logboats dating to the Neolithic discovered (Rogers, 2011:196), strongly suggesting that the polished stone axe is the minimum technology needed for their production. Even so, the number of oak logboat finds in Britain and Ireland increases dramatically with the Bronze Age (Lanting, 1997-1998), suggesting that processing with even the best stone tools remained difficult.

The shift toward oak in the Neolithic was “probably connected with a preference for longlasting wood” (Lanting, 1997-1998:645). Oak is extremely durable and rot-resistant (Boulton and Jay, 1944:54), but so, too, are some other woods. Alder is notably rot-resistant in wet environments, and Scots pine is also moderately durable (Boulton and Jay, 1944: 37-38, 90).

While durability is a desirable quality, it may come at an associated cost. Less durable timber may be more economical overall if it costs less to purchase and can be worked more quickly into a finished boat. Using published case histories (Goodburn and Redknap, 1988:19-20; Gilmore, et al, 2002:20-25), the author has compared the time required to build logboats in oak and a softer species. The unpublished results indicate that softer woods can be converted into finished logboats with less labour – a conclusion supported by common sense.

The importance of oak’s proverbial strength is also questionable. A logboat is a monocoque structure with a great deal of inherent strength, and it is not clear that small logboats built of woods of lesser strength would be more prone to breakage in use. Splitting, not shear failure, appears to be the most common form of breakage, as many archaeological oak logboats exhibit repairs made to splits that occurred while the boats remained in use (McGrail, 1978a, 1978b; Mowat, 1996; Gregory, 1997; Fry, 2000) (Figure 2). Oak is “very prone to split and check” (Boulton and Jay, 1944:55). Alder, lime, poplar, and Scots pine are all less prone to splitting (Boulton and Jay, 1944:37, 52, 59, and 89). Neither alder nor lime are strong woods; but poplar is “fairly strong for its weight,” and Scots pine, while variable, can be notably strong (Boulton and Jay, 1944:37, 52, 59, 89).

Figure 2
The logboat from Ballinphort, Ireland
The logboat from Ballinphort, Ireland, had repaired cracks in the bottom and port side. (image: Gregory, 1997:280/fig.4)

Oak’s weight is another liability. A boat of lime, a less dense and therefore more buoyant wood (~35 lb./cu.ft. vs. ~45 lb./cu.ft., Boulton and Jay, 1944:52, 54), would have higher freeboard and greater loading capacity than an equivalent one of oak. With identical loads, the lime boat would be lighter and thus easier to maneuver (Gregory, 1997:166) both on and off the water.

Location

The final functional consideration in the selection of logboat timber is its location (McGrail, 1978a:117). Obviously, this is related to the previous discussion of availability within the surrounding environment. Here, however, I will discuss location in terms of its implications for the builder.

By the late Bronze Age, Britain had undergone significant deforestation (Hooke, 2010:113-121). This, combined with oak’s natural rarity in some regions, must have made it even more difficult of access and costly. The smaller average size of Scottish than English logboats (Mowat, 1996:125) and the occasional use of washstrakes to increase their freeboard (Mowat, 1996:123) (a feature present on but a single English example (McGrail, 1978a:313)) may reflect a shortage of timber of adequate size.

In most situations of this nature, woodworkers choose alternative timber. “Trees are more interchangeable than is often supposed, and people adapt their carpentry to the trees at their disposal rather than vice versa,” writes Rackham (1980:7). “Most of the work traditionally done by oak, ash, elm, hazel, and beech in England is done in the Alps by larch, spruce, and two species of pine and in north Norway by birch alone.”

Rackham was writing of wood use in general, but the principle applies to logboats in particular. In the absence of oak, other hardwoods and softwoods were used to build logboats in Scandinavia (Eskerod, 1956, cited in Gregory, 1997:19; McGrail, 1978a:28-29). When their preferred tree species became locally unavailable late in the 20th century, the Maijuna people in the Peruvian Amazon adapted by using at least seven alternative species and going so far as to change construction methods and boat design to make best use of the new woods (Gilmore et al, 2002:13-18).

In contrast, where oak was rare or absent in the England, it was imported from other parts of the island (Rackham, 1980:164). “Man uses all sorts and sizes of timber available, and will import them if they are not available locally” (Quelch, 2005:104). It is unclear oak was ever moved long distances within Britain specifically for logboat construction, but this would appear so at least in the case of the Scottish Highlands, where oak did not grow. It is possible, however, that finished oak logboats, not oak timbers, were imported to the Highlands.

It is a surely coincidence that the percentage of timber comprised by oak in ancient English buildings – 97% (Rackham, 1980:145) – aligns so closely with the percentage of oak in the logboat record of Britain and Ireland – 96.5% (see Table 1) – but the overwhelming dominance of oak in both contexts is probably related. That builders of buildings and logboats in many parts of Britain were apparently willing to incur the additional expense of imported oak when other functionally suitable genera were available locally, and that such a practice persisted for so long, suggests motivation of an ideological nature.

Oak’s Ideological Implications

An abundance of tree- and wood-related symbolism, folklore, and religious practices attest to the material’s widespread ideological significance throughout European pre/history. Sacred groves and trees – entire species as well as individual trees – appear in ancient Greek, Roman, Germanic, and Celtic history and myth, and particularly in those of Britain and Ireland (Dowsett, 1942:101; Hooke, 2010:10-11).

Oak was only one of the trees held sacred in Britain and Ireland, along with ash, elder, whitethorn, hawthorn, hazel, and yew (Hooke, 2010:13-14, 98, 103-104, 244-245; Mac Coitr, 2010:8-11). Oak was associated with qualities such as life, strength, long or eternal life, kingship, and “the sacred,” but so were others (Mac Coitr, 2010:61-68). Of five great legendary trees in Irish mythology, one was oak, one was yew, and three were ash (Hooke, 2010:13).

But in many respects, oak has played the starring role in the sylvan culture of Britain, if somewhat less so in Ireland (Hooke, 2010:193-195). It was used symbolically in much ritual architecture, including timber circles (Hooke 2010:7-8), cathedrals (Hadfield, 1974:127), and in mortuary contexts (e.g., Evans and Hodder, 2006:192). Oak is prominent in folklore, myth, lore, and legend throughout British culture, examples including:
  • Celebrations featuring symbolic use of oak, including Beltane and Samhain (Dowsett, 1942:99-100) and the Yule log (Miles, 2013:82-83)
  • Gospel oaks (Miles, 2013:83-84)
  • a wide range of “sayings and beliefs,” for example, “Great oaks from little acorns grow.” (Miles, 2013:90-91, 110)
  • thousands of place-names incorporating variants of the word “oak” (Hadfield, 1974:174; Nelson and Walsh, 1993, cited in Mac Coitr, 2010:21; Hooke, 2010:167, passim)
  • the tale of Charles II hiding in an oak after the Battle of Worcester, and the roughly 600 pubs named “Royal Oak” in commemoration of the event, plus Royal Navy ships of that name, and Royal Oak Day (Miles, 2013:85-87, 108-109) (Figure 3)
  • depictions of oak leaves on coins and on various military medals and insignia (Miles, 2013:109)
  • dozens of named trees, famous for their size, longevity, or role in history or legend (Miles, 2013)
  • “Hearts of Oak” – the official quick-march of the Royal Navy and a symbol of its sailors – and the patriotic symbolism represented by the “wooden walls” of England’s largely oak-built sailing navy. 

Figure 3
"Royal Oak" signboards from pubs
Hundreds of “Royal Oak” establishments attest to the tree’s special role in Britain’s culture and collective psyche. (image: Miles, 2013:108).
Miles, cited above, is no scholar, but the very existence of books like his and others’ about British oaks for a popular reading audience is yet more evidence of the reverence in which the oak is held.

On the other hand, oak was also used widely throughout pre/history for the most mundane affordances, including causeways, livestock enclosures, charcoal, tools, tanning, pig feed, barrel staves, and fish-smoking (Miles, 2013:14, 23). On a superficial view, these mostly destructive or temporary applications hardly appear to reflect reverence for the material.

One must be cautious, though, of imposing a contemporary worldview on the past. “Modern, Western perceptions of trees and timber will differ from those (of the past)” (Bintley and Shapland, 2013:5). The nature of the sacred residing in the archaeological mundane is eloquently expressed by Mac Coitr:

“Taking an example unrelated to trees, the Plain (sic) Indians of North America regard the buffalo as sacred, since it provides them with food from its meat, clothing and shelter from its hide, and various implements from its bones. It is seen as a gift from the Creator, imbued with supernatural powers, sacred because of its many important practical uses, not despite them. In the same way the oak was regarded as particularly favoured by the gods due to its many valuable attributes. The distinction between the sacred and the practical, therefore, is a very modern approach and it is inappropriate to project the distinction onto people who would not have understood it” (2010:5).

Among oaks’ several symbolic meanings are strength, steadfastness, longevity, courage, dignity, abundance, and nobility (Hooke, 2010:104; Mac Coitr, 2010:16-17; Miles, 2013:14). In various contexts, it has been associated with Christianity, unredeemed paganism, fertility, and nature in general (Hooke, 2010:99-100). Most of these associations are positive, but they are also diverse.

“Problems are encountered … when wood species are attributed so many powers, symbolic meanings, and uses as status indicators that it would seem impossible to unravel which precise or multiple motive induced the use of a certain wood. This applies especially to the most common species of wood …” such as oak (Therkorn et al., 1984:362).

Given their likely priorities of strength and durability in logboats (separate from the question of whether softer woods might be suitable in these regards), it seems probable that logboat builders and owners were influenced by oak’s symbolic strength and steadfastness. Beyond that, reliable conclusions about the “meaning” of oak in logboats are probably not possible.

Historical Implications

Influenced by its symbolism, British and Irish logboat builders might have attributed to oak greater functional superiority over other wood types than was warranted. This might have caused them to overlook the affordances of other genera and may help explain the disappearance of the logboat from the islands.

Logboats disappeared from Scotland and Ireland sometime after the middle of the eighteenth century – about the same time that Ireland became almost entirely deforested and Scotland was denuded of deciduous trees, including oak (Gregory, 1997:56). While this would inevitably have killed off the craft in Ireland, the Scots might have, but did not, avail themselves of the remaining alternative of Scots pine. Was this due to the belief that oak was the only suitable timber for logboats?

The situation south of Scotland is less clear. The latest scientifically dated English logboat dates to 410 +60 BP (Lanting, 1997-1998:629/table 2) – i.e., a century or two earlier than the latest evidence for Ireland and Scotland. Although large areas of England were deforested by this time, huge amounts of oak, much of it imported, continued to be used in buildings and ship construction well into the 19th century (see, for example, Oster, 2015:3‑4 for Royal Navy timber consumption and imports). The end of logboat use in England therefore appears to be unrelated to availability, although increased cost may have been an issue.

Throughout Britain and Ireland, the near-exclusive use of oak may have constrained not only logboat size, but also boat designs and construction techniques. Softer timbers, including poplar and some pines, can be used to build expanded logboats. Wider than an unexpanded boat built from the same log, an expanded logboat is more stable, and thus better suited to certain uses (McGrail, 1998:66-70). Although expansion results in lower freeboard, this can be overcome by the addition of washstrakes (Figure 4). A simple “dugout” can thus become the basis for a larger and more capable boat, and expanded-extended logboats are known from many cultures (Johnstone, 1980:47-51). The British commitment to oak, which is generally thought not to be expandable, foreclosed this line of development. (See, however, Black, ND.) Likewise, because green oak does not burn, British logboat builders never had the luxury of using fire as a tool to make hollowing the log easier (Gregory, 1997:258). Whether these affordances of other woods would have been explored in Britain in the absence of a near-exclusive commitment to oak is, of course, unknowable.

Figure 4


Top: carved but unexpanded. Center: expansion in process. Bottom: washstrakes being added
Stages in construction of an expanded-extended logboat. Top: carved but unexpanded. Center: expansion in process to increase beam. Bottom: washstrakes being added to raise freeboard. (images: Johnstone, 1980:49-50/figures 5.5, 5.6, 5.7)

Summary and Conclusions

This paper noted the predominance of oak in the logboat record of Britain and Ireland and posited a variety of possible explanations. Lack of available timber options, preferential preservation in the archaeological record, and oak’s superior engineering characteristics were considered. These explanations were found to be false or inadequate, leaving ideologically-based preference as the remaining explanation.

Trees in general were shown to have profound spiritual implications throughout pre/history and cross-culturally, and some of the symbolic qualities associated with oak were discussed. It was suggested that the symbolic association between oak and the qualities of strength and durability was a likely factor influencing its preferred status in logboats.

Finally, the implications for logboat design and construction were discussed, and it was suggested that the near-exclusive commitment to oak in Britain and Ireland might have limited the technological development of the logboat type and associated construction methods.

# # #

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